PROJECT SUMMARY: In its recently released report, Improving Diagnosis in Health Care, the Institute of Medicine (IOM) highlighted that most individuals will experience at least one diagnostic error in their lifetime, sometimes with devastating consequences. Compared to other healthcare settings, clinicians working in emergency departments (EDs) are particularly vulnerable to making diagnostic errors due to time-pressured decision-making in a busy and often chaotic environment. In addition to this, provision of emergency care to children is complicated by their unique needs such as weight-based dosing of medications, their inability to verbalize their symptoms and often, their dependence on parents/guardians even for accessing healthcare. There are approximately 25 million annual pediatric ED visits in the United States. A conservative estimate of 5% prevalence, translates into ~ 1.25 million potential annual cases of diagnostic errors in the pediatric ED. To date, there has been no systematic research on diagnostic errors in the pediatric emergencies. Diagnostic errors, when defined as the inability to make a correct or timely diagnosis based on available evidence (i.e. missed opportunities for improving diagnosis or MOIDs), have been investigated in adult, outpatient settings. Members of our research team have used electronic health record based triggers to detect MOIDs and study the factors that cause diagnostic errors. Our long-term goal is to better understand MOIDs in pediatric EDs to ultimately decrease their prevalence. To accomplish that, in this project, we will assemble a multidisciplinary panel of experts in diagnostic decision making, pediatric emergency medicine along with patient/family advisory boards to develop a pediatric ED relevant model to identify triggers and subsequently use them to measure the frequency as well as contributing factors of diagnostic errors in four pediatric EDs. Our project is significant, innovative, and timely because it will lay the foundation for development of error detection tools that can be used to provide timely feedback to clinicians, track institutional or clinician performance, and measure impact of error mitigation strategies.